Pipe bend having longitudinal folds



Sept. 1, 1964 F. PENSOTTI PIPE BEND HAVING LONGITUDINALFOLDS Filgad Jan. 6, 1961 FIG. I.

FIG. 3

INVEN TOR.

United States Patent 3,146,797 PEPE BEND HAVENG LONGITUDENAL FOLDS Franco Pensotti, Via Roma 8, Legnano, Italy Filed Jan. 6, 1961, Ser. No. 81,028 Claims priority, application Italy Feb. 12, 1960 1 Claim. (Cl. 138-68) Many bends and pipe bends are useful for heat exchanger units.

The engineering requirement and economic necessity of concentrating the greatest possible heat-exchange surface area in the smallest possible volume is achieved satisfactorily to the extent that the radii of curvature used to connect up the parts or of the parts themselves are kept as small as possible.

When cold bending, the minimum radius of curvature attainable is limited by mechanical requirements, while hot bending is expensive and requires pipe having heavy thickness.

Cold bending of standard thickness pipe to small radii or curvature and with folds or Wrinkles formed at right angles to the plane in which the curve lies is already known in practice. This type of bend, though, presents a noticeable resistence to the flow of liquids inside, leading to the creation of eddies, and the stopping of bubbles, with resulting corrosion or formation of scale in the area of the bend.

The bend being considered may be also made cold, with small radii of curvature, starting from standard-size pipe, without any special material, without the crosswise folds or wrinkles and, nevertheless, with radii of curvature which are smaller than any which have been achieved to date under the same conditions.

This invention gives the above described advantages, since it causes one or more folds or recesses to form in a longitudinal direction, parallel to the axis of the pipe along the inside of the bend during the bending process.

This invention provides for the longitudinal fold or folds to start before the point where the bend begins, to

3,146,797 Patented Sept. 1, 1964 ice continue through the bend and to end at a point after the end of the bend, and that the depth of the fold or folds will gradually increase until the halfway point of the angle of curvature is reached, thereafter decreasing until it disappears.

The excess material accumulating on the inside of the curve is thus used to make up the walls of the longitudinal fold or folds.

FIGS. 1, 2 and 3 show three schematic projections of the principal parts of an example of a pipe bend obtained in accordance with the invention.

The pipe bend, as shown, includes straight portions 1, 2 and a bentportion 3. The bent portion is provided with a longitudinal fold or recess 4 whose depth at the beginning 5 of the curvature is zero, but gradually increases to the mid-point 6 of the angle of curvature; that is, the depth of the recess then gradually decreasing to Zero at the end 7 of the bent portion.

What I claim is:

A tube for use in a heat exchanger or the like comprising a tubular member having spaced ends and a bend interconnecting said ends, said bend being intermediate said ends which are disposed parallel and adjacent each other, said bend being defined by an inner curvature, a longitudinal recess formed in said bend along the inner curvature and concentric to the axis of the tubular member whereby resistance to a fluid flow in the tubular member is substantially reduced, said recess having a maximum depth at the mid-point of the inner curvature, and said recess gradually terminating in depth from the mid-point toward each end of the inner curvature whereby creation of eddy currents and corrosion of the tubular member is minimized in areas of the bend.

References Cited in the file of this patent UNITED STATES PATENTS 2,016,720 Kraus Oct. 8, 1935 2,080,626 Mojonnier May 18, 1937 2,960,114 Hinde Nov. 15, 1960 

